/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.objectweb.asm.signature;

import org.objectweb.asm.Opcodes;

/**
 * A SignatureVisitor that generates signature literals, as defined in the Java Virtual Machine
 * Specification (JVMS).
 *
 * @see <a href="https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.9.1">JVMS
 *     4.7.9.1</a>
 * @author Thomas Hallgren
 * @author Eric Bruneton
 */
public class SignatureWriter extends SignatureVisitor {

    /** The builder used to construct the visited signature. */
    private final StringBuilder stringBuilder;

    /** Whether the visited signature contains formal type parameters. */
    private boolean hasFormals;

    /** Whether the visited signature contains method parameter types. */
    private boolean hasParameters;

    /**
      * The stack used to keep track of class types that have arguments. Each element of this stack is
      * a boolean encoded in one bit. The top of the stack is the least significant bit. The bottom of
      * the stack is a sentinel element always equal to 1 (used to detect when the stack is full).
      * Pushing false = {@code <<= 1}, pushing true = {@code ( <<= 1) | 1}, popping = {@code >>>= 1}.
      *
      * <p>Class type arguments must be surrounded with '&lt;' and '&gt;' and, because
      *
      * <ol>
      *   <li>class types can be nested (because type arguments can themselves be class types),
      *   <li>SignatureWriter always returns 'this' in each visit* method (to avoid allocating new
      *       SignatureWriter instances),
      * </ol>
      *
      * <p>we need a stack to properly balance these angle brackets. A new element is pushed on this
      * stack for each new visited type, and popped when the visit of this type ends (either in
      * visitEnd, or because visitInnerClassType is called).
      */
    private int argumentStack = 1;

    /** Constructs a new {@link SignatureWriter}. */
    public SignatureWriter() {
        this(new StringBuilder());
    }

    private SignatureWriter(final StringBuilder stringBuilder) {
        super(/* latest api =*/ Opcodes.ASM9);
        this.stringBuilder = stringBuilder;
    }

    // -----------------------------------------------------------------------------------------------
    // Implementation of the SignatureVisitor interface
    // -----------------------------------------------------------------------------------------------

    @Override
    public void visitFormalTypeParameter(final String name) {
        if (!hasFormals) {
            hasFormals = true;
            stringBuilder.append('<');
        }
        stringBuilder.append(name);
        stringBuilder.append(':');
    }

    @Override
    public SignatureVisitor visitClassBound() {
        return this;
    }

    @Override
    public SignatureVisitor visitInterfaceBound() {
        stringBuilder.append(':');
        return this;
    }

    @Override
    public SignatureVisitor visitSuperclass() {
        endFormals();
        return this;
    }

    @Override
    public SignatureVisitor visitInterface() {
        return this;
    }

    @Override
    public SignatureVisitor visitParameterType() {
        endFormals();
        if (!hasParameters) {
            hasParameters = true;
            stringBuilder.append('(');
        }
        return this;
    }

    @Override
    public SignatureVisitor visitReturnType() {
        endFormals();
        if (!hasParameters) {
            stringBuilder.append('(');
        }
        stringBuilder.append(')');
        return this;
    }

    @Override
    public SignatureVisitor visitExceptionType() {
        stringBuilder.append('^');
        return this;
    }

    @Override
    public void visitBaseType(final char descriptor) {
        stringBuilder.append(descriptor);
    }

    @Override
    public void visitTypeVariable(final String name) {
        stringBuilder.append('T');
        stringBuilder.append(name);
        stringBuilder.append(';');
    }

    @Override
    public SignatureVisitor visitArrayType() {
        stringBuilder.append('[');
        return this;
    }

    @Override
    public void visitClassType(final String name) {
        stringBuilder.append('L');
        stringBuilder.append(name);
        // Pushes 'false' on the stack, meaning that this type does not have type arguments (as far as
        // we can tell at this point).
        argumentStack <<= 1;
    }

    @Override
    public void visitInnerClassType(final String name) {
        endArguments();
        stringBuilder.append('.');
        stringBuilder.append(name);
        // Pushes 'false' on the stack, meaning that this type does not have type arguments (as far as
        // we can tell at this point).
        argumentStack <<= 1;
    }

    @Override
    public void visitTypeArgument() {
        // If the top of the stack is 'false', this means we are visiting the first type argument of the
        // currently visited type. We therefore need to append a '<', and to replace the top stack
        // element with 'true' (meaning that the current type does have type arguments).
        if ((argumentStack & 1) == 0) {
            argumentStack |= 1;
            stringBuilder.append('<');
        }
        stringBuilder.append('*');
    }

    @Override
    public SignatureVisitor visitTypeArgument(final char wildcard) {
        // If the top of the stack is 'false', this means we are visiting the first type argument of the
        // currently visited type. We therefore need to append a '<', and to replace the top stack
        // element with 'true' (meaning that the current type does have type arguments).
        if ((argumentStack & 1) == 0) {
            argumentStack |= 1;
            stringBuilder.append('<');
        }
        if (wildcard != '=') {
            stringBuilder.append(wildcard);
        }
        // If the stack is full, start a nested one by returning a new SignatureWriter.
        return (argumentStack & (1 << 31)) == 0 ? this : new SignatureWriter(stringBuilder);
    }

    @Override
    public void visitEnd() {
        endArguments();
        stringBuilder.append(';');
    }

    /**
      * Returns the signature that was built by this signature writer.
      *
      * @return the signature that was built by this signature writer.
      */
    @Override
    public String toString() {
        return stringBuilder.toString();
    }

    // -----------------------------------------------------------------------------------------------
    // Utility methods
    // -----------------------------------------------------------------------------------------------

    /** Ends the formal type parameters section of the signature. */
    private void endFormals() {
        if (hasFormals) {
            hasFormals = false;
            stringBuilder.append('>');
        }
    }

    /** Ends the type arguments of a class or inner class type. */
    private void endArguments() {
        // If the top of the stack is 'true', this means that some type arguments have been visited for
        // the type whose visit is now ending. We therefore need to append a '>', and to pop one element
        // from the stack.
        if ((argumentStack & 1) == 1) {
            stringBuilder.append('>');
        }
        argumentStack >>>= 1;
    }
}
